In Canadian Pat. No. 950,853 issued July 9, 1974 and assigned to a common assignee, an air conveyor was described and claimed, one embodiment of the conveyor utilizing a concave, trough-like track with a plurality of nozzles therein. The nozzles were asymmetrically positioned parallel to the center-line of the track and were directed at an angle to the center-line with respect to a tangent at the track surface. When an article to be conveyed, such as a roll of toilet tissue or a roll or paper towelling, was placed in the track and subjected to high velocity air flowing from the nozzles the article was displaced from a rest position coaxial with the track to a position slightly to one side of the center-line and was supported on the thin film of the issuing air which adhered to the curved track surface. In effect, the supporting air film formed a wedge of supporting fluid between the concave surface of the track and the convex surface of the supported article. The stability of this system has proven to be extremely good and the power requirement has proven to be very small.
Another Canadian patent (No. 1,002,565 issued Dec. 28, 1976 to the same inventor as in the previously identified patent) disclosed and claimed an up-scale version of the basic conveyor system, that invention being a vehicular transportation system using either one or two parallel tracks and a vehicle having appropriate mating support surfaces for support in or on the track(s).
In the first-identified patent mention was made of a conveyor system utilizing tracks laid in the floor of a factory with the supported article being a plate arrangement having a lower surface complementary to the track whereby commodities to be handled in the factory would be positioned on the uppermost surface of the plate and moved along the track in the factory floor to a new location, such as the loading dock. This concept is basic to a warehousing system and can be extended even beyond the warehouse to transport trailers, rail cars and aircraft that might carry the merchandise from the factory or warehouse to the distributor or to the eventual consumer.
This extension of the basic conveyor concept from the situation where the article positioned in the track is the actual product to the situation where the article positioned in the track supports the actual product requires considerations not previously deliberated upon in great detail. The product support could be a pallet or even a belt adapted to ride in the track. For example the question of stability suggests that a two-track conveyor is desirable for a pallet, as does the question of very heavy loads, weight distribution and power requirements to establish lift. A single track would be satisfactory for supporting a belt. Also durability and flexibility of the track and support should be considered as should the question of cushioning when the product is fragile.
The question of load shocks and cyclical or variable track support forces becomes more paramount when the concept of a warehouse converyor or distribution system is extended to the common carriers such as transport trailers. In many instances it would be desirable for a load, moving on an air supported pallet in the warehouse, to remain on the pallet and to pass directly, without the need of a fork-lift truck, into a waiting carrier. Once inside the carrier the pallet would rest on its supports which in turn would be restrained within the conveyor track with the air turned off. This situation makes it very desirable to isolate the cargo or load from the carrier body as much as possible, preferably through the cushioned pallet supports.